1. Field of the Invention
This invention relates to an adapter to be mounted on the eyepiece of an endoscope, and more particularly to an adapter having the function of varying the magnification of the eyepiece.
2. Description of the Prior Art
Concerning the endoscope, a device for viewing the interior of a human body, it is highly desirable that the angle of view of the endoscope be enlarged. By enlarging the angle of view of the endoscope, the thickness of the flexible tube can be reduced. A thinner tube is highly desirable since it decreases the possibility of pain when inserted into the body.
On the other hand, by enlarging the angle of view or reducing the thickness of the tube, the size of the image observed through the eyepiece is reduced and the device's diagnostic efficiency and accuracy are lowered. Further, the eyes are likely to be easily tired viewing this reduced image, the effectiveness of forceps is lessened and cannulation into the duodeunum becomes difficult. Concerning the use of forceps, it is very difficult for doctors accustomed to handle forceps with a conventional angle of view or magnification to operate with a wide angle view.
Thus, there is now a demand for an endoscope having a wide angle view which is capable of reducing the angle of view when desired, such as times when forceps are being used.